Starting in OS X El Capitan there's a framework to protect sensitive system file...

ubernostrum on April 18, 2016 | parent | context | favorite | on: Remote code execution, git, and OS X

Starting in OS X El Capitan there's a framework to protect sensitive system files which disallows even root from modifying them. The only way to make changes is to (as root) disable that framework, then reboot, make the changes, re-enable and reboot again.